Various window shade mechanisms specifically adapted for aircraft windows have been previously presented. One such shade mechanism utilizes cables and pulleys. See U.S. Pat. No. 5,082,043. A slidable actuator must be manually moved to operate the window shade. Manual operation is inconvenient. Also, during flight it is advantageous to have the capability of operating all the window shades on an aircraft simultaneously by one person. However, this is not possible with manually-operated window shades. Further, various parts of the shade mechanism are particularly vulnerable to malfunction. Moreover, many components are required, which reduces reliability and increases the cost of producing the shade mechanism.
Another shade mechanism involves a motor that is fixed inside the window and operates the shade with cables and pulleys. See U.S. Pat. Nos. 5,515,898 and 4,998,576. This mechanism also requires numerous components, which can only be manufactured, assembled, and installed at considerable cost. Further, because of the numerous parts, the reliability of the design is questionable.
Still another shade mechanism involves a motor attached to a lower bar or rail of a shade. The motor moves along with the shade as the shade is extended and retracted. See U.S. Pat. No. 4,807,686. However, this shade mechanism also utilizes numerous components, which increases the cost of production and reduces the reliability of operation.
A further shortcoming of at least some of the above-mentioned designs is too much bulk and weight. The space available in an aircraft window within which the entire window shade assembly must fit is quite restricted. Also, reduction of weight is of particularly high importance in an aircraft environment.
U.S. Pat. No. 6,186,211 discloses a motorized window shade assembly for operating a window shade having a rail attached to one end of the shade to extend and compress the shade with movement of the rail. The motorized window shade assembly includes a shell having two sidewalls, and a rail extending between the two sidewalls of the shell. The sidewalls have respective opposed inner surfaces with a channel therein, shoulders adjacent and perpendicular to the inner surfaces, respectively, and a traction surface on each of the shoulders. An axle is rotatingly coupled to the rail and has a traction wheel coupled to each end thereof. Opposite tips of the axle ride within the channels in the sidewalls, and the traction wheels engage the traction surface. A motor is attached to the rail and is drivingly coupled to the axle. Although this is a useful and effective arrangement, its size does not readily fit within the space limitations available in windows used on many commercial airliners. Thus, it became necessary to devise a motorized window shade assembly with the advantages of this configuration, but with smaller stack height (the extent to which the shade is compressed when fully retracted), width and thickness.